1. Field of the Invention
The invention generally concerns a measurement device with a sensor for capturing the contents and/or characteristics of components of agricultural crops.
2. Related Technology
Measurement devices suitable for analyzing the contents of organic material comprise, as a rule, sensors that work with light in the near-infrared wavelength rate in a reflection (NIR) or transmission (NIT) mode and are provided with light sources and optical analyzers. Several kinds of measurements devices of these types have been recommended for application to harvesting machines in order to capture and document the characteristics of the crop.
Harvesting machines with these kinds of measurement devices have been described, for example, in WO 99/46974 A, WO 99/40419 A, WO 00/00818 A, EP 1 053 671 A, and in C. von Rosenberg et al: “A Rugged Near-infrared Spectrometer for the Real-time Measurement of Grains during Harvest,” Spectroscopy 15/6 (2000). The measurement devices are each arranged near a conveyor channel of the harvesting machine, through which the crop flows or is conveyed. In DE 012 36 515 C, a measurement device of this kind is applied to the wall of a chamber that is filled with a crop sample taken from the main crop flow by screw conveyor.
In the known measurement devices, a window having a transparent pane is arranged between the actual measurement device and the crop flow to permit light to travel through the window and to prevent the crop from doing the same and passing into the interior of the measurement device. The pane is arranged, as a rule, so as to be level with the wall of the conveyor channel. Under certain conditions, this positioning has the disadvantage that the pane becomes dirty from adhering crop or other impurities, such as dust or debris, so that optical measurement of the crop can no longer occur because the pane is obstructed by crop or other debris adhered thereto. For example, the dust or debris may prevent reflection and/or reception of the sensor transmission. As another example, the crop adhered to the pane may cause false or misleading readings, particularly if the crop adhered to the pane is different from the crop moving below.
In WO 00/00818 A, the pane is inclined in one embodiment at an angle of 5 to 10° with respect to the surface of the measurement device and the conveyor channel and protrudes somewhat beyond the surface of the measurement device into the conveyor channel. Through this angle, it is intended to achieve that light from the light source of the measurement device that passes through and is reflected by the pane does not arrive at the detector. The pane is arranged so as to be stationary and impurities can accumulate on the pane. In an embodiment in which the pane protrudes permanently into the crop flow, a strong wear occurs on the pane through the constant contact with the crop flow, if a special wear-resistant material is not used.
The problem of impurities on the sensor surface is also present in sensors that do not work optically. Thus, a measurement chamber is recommended in DE 197 44 485 A in which the crop is studied by a capacitative sensor that captures moisture, through which a movable element is forced to be emptied and cleaned. In DE 197 44 481 A, it is recommended that the sensor be applied to the wall of a screw conveyor to the conveyor windings of which cleaning elements are applied. JP 57 014 848 A describes a sensor for capturing grain moisture that captures the conductivity of grains arranged by means of two electrodes arranged in a conveyor channel. One of the electrodes is moved before and after a measurement, in order to create contact between the grains adhering to the electrode and the grains in the conveyor channel, and the electrodes are thereby cleaned. These solutions are not suitable, however, for sensors whose sensitive surfaces are arranged on the wall of a conveyor channel in which the crop is not transported by a separate conveyor, but only accelerated at the start of the conveyor channel by blowing or something similar.